linux-kernel - Re: [PATCH 1/3] drm/bridge: samsung-dsim: move bridge init sequence to atomic

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Message-Id: <DG3ORZIEYI9Z.34Z2QZ4J2A21@disroot.org>
Date: Sun, 01 Feb 2026 19:44:24 +0530
From: "Kaustabh Chakraborty" <kauschluss@...root.org>
To: "Marek Szyprowski" <m.szyprowski@...sung.com>, "Kaustabh Chakraborty"
 <kauschluss@...root.org>, "Inki Dae" <inki.dae@...sung.com>, "Jagan Teki"
 <jagan@...rulasolutions.com>, "Andrzej Hajda" <andrzej.hajda@...el.com>,
 "Neil Armstrong" <neil.armstrong@...aro.org>, "Robert Foss"
 <rfoss@...nel.org>, "Laurent Pinchart" <Laurent.pinchart@...asonboard.com>,
 "Jonas Karlman" <jonas@...boo.se>, "Jernej Skrabec"
 <jernej.skrabec@...il.com>, "Maarten Lankhorst"
 <maarten.lankhorst@...ux.intel.com>, "Maxime Ripard" <mripard@...nel.org>,
 "Thomas Zimmermann" <tzimmermann@...e.de>, "David Airlie"
 <airlied@...il.com>, "Simona Vetter" <simona@...ll.ch>
Cc: <dri-devel@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>,
 <stable@...r.kernel.org>
Subject: Re: [PATCH 1/3] drm/bridge: samsung-dsim: move bridge init sequence
 to atomic_enable

On 2026-01-26 09:57 +01:00, Marek Szyprowski wrote:
> On 24.01.2026 18:20, Kaustabh Chakraborty wrote:
>> Since commit c9b1150a68d9 ("drm/atomic-helper: Re-order bridge chain
>> pre-enable and post-disable"), pre-enable sequence is called before the
>> CRTC is enabled.
>>
>> This causes unintended side-effects (abberation among potentially other
>> things) in the display when samsung_dsim_init() is called in the
>> pre-enable part of the sequence. Call it in samsung_dsim_atomic_enable()
>> instead.
>>
>> Cc: stable@...r.kernel.org # v6.17 and later
>> Signed-off-by: Kaustabh Chakraborty <kauschluss@...root.org>
>
> I'm not sure if this will be needed:
>
> https://lore.kernel.org/all/20251205-drm-seq-fix-v1-0-fda68fa1b3de@ideasonboard.com/

Tested on v6.19-rc7, this is fixed now. This can be dropped.

>
>
>> ---
>>   drivers/gpu/drm/bridge/samsung-dsim.c | 13 +++++++------
>>   1 file changed, 7 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
>> index 1d85e706c74b9..975f8b50ae660 100644
>> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
>> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
>> @@ -1655,6 +1655,13 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
>>   	}
>>   
>>   	dsi->state |= DSIM_STATE_ENABLED;
>> +}
>> +
>> +static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
>> +				       struct drm_atomic_state *state)
>> +{
>> +	struct samsung_dsim *dsi = bridge_to_dsi(bridge);
>> +	int ret;
>>   
>>   	/*
>>   	 * For Exynos-DSIM the downstream bridge, or panel are expecting
>> @@ -1665,12 +1672,6 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
>>   		if (ret)
>>   			return;
>>   	}
>> -}
>> -
>> -static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
>> -				       struct drm_atomic_state *state)
>> -{
>> -	struct samsung_dsim *dsi = bridge_to_dsi(bridge);
>>   
>>   	samsung_dsim_set_display_mode(dsi);
>>   	samsung_dsim_set_display_enable(dsi, true);
>>
> Best regards